Classification:
According to whether it is even, it can be divided into odd and even numbers.
1, the first odd number: numbers that are not divisible by 2 are called odd numbers.
2. The second even number: a number divisible by 2 is called an even number. That is to say, except odd numbers, they are all even numbers.
Note: 0 is an even number. In 2002, the International Mathematical Association stipulated that zero is an even number. In 2004, China also stipulated that zero is an even number. Even numbers can be divisible by 2, and so can 0, but numbers are still 0.
According to the number of factors, it can be divided into prime number, composite number, 1 and 0.
1, prime number: only 1 and its own natural number are called prime numbers. Also known as prime numbers.
2. Composite number: a natural number with other factors besides 1, which is itself called a composite number.
3, 1, only 1 factor. It is neither a prime number nor a composite number.
4, of course, 0 can't calculate the factor, just like 1, which is neither a prime number nor a composite number.
Extended data:
Natural numbers are only integers equal to or greater than 0 (that is, 0 and positive integers), so there are countless natural numbers, usually represented by n?
Pinyin z? rán？ shù？
English translation is natural? Number; ? The whole? Number?
The set of all non-negative integers? Commonly used? n？ show
Natural numbers play a great role in daily life, and people use them widely. Natural numbers are the earliest numbers in human history, which are widely used in counting and measurement. People often use natural numbers to mark or classify things, such as bus routes, house numbers, postal codes, etc.
Historically, there have been two views on whether 0 is a natural number in mathematics circles at home and abroad: one thinks that 0 is a natural number, and the other thinks that 0 is not a natural number. Since the founding of the People's Republic of China, textbooks for primary and secondary schools in China have always stipulated that natural numbers do not include 0. At present, most foreign mathematicians stipulate that 0 is a natural number. In order to facilitate international communication, People's Republic of China (PRC) national standard (GB 3 100-3 102-93), quantity and unit (1 1-2.9) was promulgated in 1993.
The set of all nonnegative integers is called nonnegative integer set, that is, natural number set. ) When counting objects, the number of 0. 1.2.3.4.5.6.7.8.9 is called a natural number. Natural numbers have two meanings: quantity and order, which are divided into cardinal number and ordinal number. Basic unit: 1 Counting unit: one, ten, one hundred, one thousand, ten thousand and one hundred thousand. ......
Sequences 1, 2, 3, 4, 5, 6, 7, 8, 9, 10,1,12, ... n are called natural sequences. The nature series does not include 0. ?
The general formula of natural sequence an = n?
The sum of the first n terms of a natural sequence Sn=n(n+ 1)/2. ? Sn=na 1+n(n- 1)/2？
The natural sequence is essentially a arithmetic progression, with the first term a 1= 1 and the tolerance d= 1.
References:
Baidu Encyclopedia-Concept of Natural Numbers